Tool to measure white noise on a cat 5 cable?

neotechnet

neotechnet

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Hi all, basically we have a situation where a client's POS company is getting corrupted data from their terminals to the onsite server. They are saying it might be interference from electrical wiring crossing with network wiring in the ceiling aka "white noise".

The problem with this corruption is intermittent so it's not constant or daily.

Is there a high end networking tool that can measure these things and tell us if there is a lot of interference with a network line especially over a period of time?

Any recommendations would be great, thanks.
 
I think I would worry less about "white-noise" and just do a simple error rate test on the line. With a relatively inexpensive tester, you can throw a lot of bits at it and see if the bits come back exactly the same way they were sent (as a function of the tester with a loopback device). If you do have a noise issue, you'll see a fairly high error rate. Assuming that this is an Ethernet/TCPIP line, I would also think that the TCP/IP protocol would alleviate noise. You should be seeing low bandwidth, as the protocol is having to resend a lot of packets. Or, in this case, the terminal will take a longer period of time to process a transaction. But the transactions would not be garbled. And if the terminals are network devices, I would tend to think that it's something on their end. But I would throw an error test at the line to "make sure" before going back to the POS company.
 
It's not called "White Noise". The correct term is electromagnetic interference (EMI). White Noise is an audio signal that has all frequencies in the audio spectrum at random levels. It is similar to Pink Noise which is all of the audio frequencies at the same level. White noise is used mostly for sound masking.

What you are talking about is a common occurrence when cabling is installed wrong. Chances are the cable is laying up against a light or dimmer somewhere in its path.

A cable analyzer aka Certifier may or may not show the problem. The best way to find this issue is using the http://enterprise.netscout.com/network-troubleshooting-tool/OneTouch-AT-Network-Assistant . This was originally made for and by Fluke for its Versiv Platform and was acquired by NetScout in October 2014 along with the rest of Flukes network monitoring lines.
 
Mercenary Roadie said:
It's not called "White Noise". The correct term is electromagnetic interference (EMI). White Noise is an audio signal that has all frequencies in the audio spectrum at random levels. It is similar to Pink Noise which is all of the audio frequencies at the same level. White noise is used mostly for sound masking.

What you are talking about is a common occurrence when cabling is installed wrong. Chances are the cable is laying up against a light or dimmer somewhere in its path.

A cable analyzer aka Certifier may or may not show the problem. The best way to find this issue is using the http://enterprise.netscout.com/network-troubleshooting-tool/OneTouch-AT-Network-Assistant . This was originally made for and by Fluke for its Versiv Platform and was acquired by NetScout in October 2014 along with the rest of Flukes network monitoring lines.
Click to expand...

But a cable analyzer will cost a lot less than the Fluke. And will, at least, tell you that you have a problem. Maybe not exactly what the problem is, but just knowing that there is a problem is better than nothing. If the line is truly installed wrong, the solution will be the same with or without the expensive equipment.

If I were a betting man, I would bet that the cable run is fine. I would try the error test, and I would even hook a computer to it and see what kind of bandwidth speeds I could get out of it. The fact that the POS company is calling it "white noise" just tells me that they don't have a clue, and the problem is really with their equipment.

A couple of questions to ask. How long has this POS system been installed? Is this a newly installed system that has had this issue from the beginning, or is it a system that has been installed a while and only recently started having an issue?
 
No need to purchase anything. Anything you need can be rented at places like https://www.atecorp.com/. You can then produce a printed test showing the cable is certified to Cat6 standard, or what ever you want. I would also test the power to the machines as well as put them on a good UPS.

But I agree with @Computer Bloke, modern networking is full of error correction processes so receiving corrupted data is virtually impossible. Personally I've run into situations where there was induced voltage in the cable run. All that happened is the transmission speeds were really slow.
 
You could also install or lend a managed switch that keeps track of packet loss. That's where I would be looking- packet loss. If it's really bad, or maybe you have a wire short or extreme interference from a nearby piece of equipment... but only intermittently, you can have problems. The network tries to resend but eventually will time out and cause issues.

Perhaps they are using the break room microwave with the door cracked open half way because it doesn't have a "medium" setting?
 
It might be worth checking the termination connections on the cable. If the twisted pairs aren't being used on the right pins, you could be getting interference that isn't cancelled out by common-mode rejection, even though the electrical connections allow the cable to work
 
neotechnet said:
Hi all, basically we have a situation where a client's POS company is getting corrupted data from their terminals to the onsite server. They are saying it might be interference from electrical wiring crossing with network wiring in the ceiling aka "white noise".

The problem with this corruption is intermittent so it's not constant or daily.

Is there a high end networking tool that can measure these things and tell us if there is a lot of interference with a network line especially over a period of time?

Any recommendations would be great, thanks.
Click to expand...

Since this is intermittent I would start by looking at the server. If you have a bad cable or the cable is picking up extreme interference then it should be pretty much constant - except to the comment of the microwave oven (I love that).

I would be checking the memory on the server, I would run some extended ping tests - the simple stuff first. If the problem only shows up during heavy use/demands then that will help narrow this down too. I really do not think you need to invest in all kinds of expensive equipment to get this figured out. The hard part is the "intermittent" issue. Your going to have to try and reproduce the issue. So, I would go to one of the terminals and send like a 1 gig file across the network to the server. See if it fails on that. Then try it from another terminal and see if it still fails. Possible areas are the network cards. Perhaps its just one of the terminals network cards are bad and thats the "intermittent" issue - just when they do something from that terminal.

As also suggested, Hook up a laptop to the network and then send a large file across to the server. Fail? Pass?

Test the server components if at all possible.

coffee
 
For your network check, WinMRT will give you some more statistical data, and track it across multiple hops (but it sounds like you're on the same subnet, correct?): http://winmtr.net/
 
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